Monitor Description
The 2 monitors, Key-off and Purge Flow, are used to detect malfunctions relating to DTCs P0441-7E, P0441-7F and P0441-9C. The key-off monitor is initiated by the ECM internal timer, known as the soak timer, 5 hours* after the ignition switch is turned off. The purge flow monitor runs while the engine is running.
HINT:
*: If the engine coolant temperature is not less than 35°C (95°F) 5 hours after the ignition switch is turned off, the monitor check starts 2 hours later. If it is still not less than 35°C (95°F) 7 hours after the ignition switch is turned off, the monitor check starts 2.5 hours later.
- KEY-OFF MONITOR
- Purge VSV stuck open
In operation C, the leak detection pump creates negative pressure (vacuum) in the EVAP system. The EVAP system pressure is then measured by the ECM using the canister pressure sensor. If the stabilized system pressure is higher than [second reference pressure x 0.2], the ECM interprets this as the purge VSV (Vacuum Switching Valve) being stuck open. The ECM illuminates the MIL and stores the DTC (2 trip detection logic).
- Purge VSV stuck closed
During sequence D, the canister pressure sensor measures the EVAP system pressure. The pressure measurement for purge VSV monitor is begun when the purge VSV is turned on (open) after the EVAP leak check. When the measured pressure indicates an increase of 0.3 kPa [0.04 psi] or higher, the purge VSV is functioning normally. If the pressure does not increase, the ECM interprets this as the purge VSV being stuck closed. The ECM illuminates the MIL and stores the DTC (2 trip detection logic).
- Purge VSV stuck open
- PURGE FLOW MONITOR
The purge flow monitor consists of 2 monitors. The 1st monitor is conducted every time and the 2nd monitor is activated if necessary.
- The 1st monitor
While the engine is running and the purge VSV is on (open), the ECM monitors the purge flow by measuring the EVAP pressure change. If negative pressure is not created, the ECM begins the 2nd monitor.
- The 2nd monitor
The vent valve is turned on (closed) and the EVAP pressure is then measured. If the variation in the pressure is less than 0.396 kPa [0.0574 psi], the ECM interprets this as the Purge VSV being stuck closed. The ECM illuminates the MIL and stores DTC P0441-9C (2 trip detection logic).
Atmospheric pressure check:
In order to ensure reliable malfunction detection, the variation in atmospheric pressure, before and after performing the purge flow monitor, is measured by the ECM.